Apparatus and process for the formation of monocrystalline silicon carbide (SiC) on a nucleus

Abstract

The invention relates to an apparatus for forming SiC on a nucleus. The apparatus comprises a first enclosure (100) defined by at least one wall (102, 110, 112) and able to receive a SiC nucleus (122), a SiC powder reservoir (118) and means (120) for heating the enclosure and, according to the invention, the wall (102, 110, 112) is essentially covered by at least one SiC layer (116).

What is claimed is: 
     
       1. A process for forming an SiC ingot in an apparatus comprising a crucible having; a first enclosure defined by a bottom, a cover and at least one interior sidewall and in which a SiC nucleus is positioned, each of the three crucible components being formed from a material selected from the group consisting of graphite, TiC, HfC, TaC and MoC; a SiC powder reservoir located within the first enclosure which provides a first SiC source; a second exterior sidewall, said first interior wall and said second exterior wall defining a clearance which is filled with SiC as a second SiC source; and a means for establishing at least one temperature gradient between the SiC nucleus and the first and second SiC sources, the process, comprising: a) placing said SiC nucleus in said first enclosure;   b) forming a vacuum within said first enclosure;   c) cleaning said nucleus; and   d) growing a body of SiC on said nucleus.     
     
     
       2. The process of claim 1, wherein during the cleaning (c) of said nucleus the temperatures Tg, Ts and Tc respectively of the nucleus, the SiC material within said first enclosure and the SiC material within said clearance such that Tg>Ts and Tg>Tc. 
     
     
       3. The process of claim 1, wherein during the growth of SiC on said nucleus, temperatures Tg, Ts and Tc respectively of said nucleus, the SiC material within said first enclosure and the SiC material within said clearance are such that Ts>Tc>Tg. 
     
     
       4. The process of claim 1, wherein, prior to the formation of the vacuum within the first enclosure, at least one silicon shim is placed at the top of said exterior side wall and under the cover of the crucible, and, subsequent to vacuum formation, the silicon shim is melted which seals the cover to said sidewall. 
     
     
       5. The process of claim 1, wherein during the growth of SiC on said nucleus, the temperature of said nucleus ranges from 2,000 to 2240° C. and the temperature of the SiC powder in said reservoir ranges from 2200 to 2350° C. 
     
     
       6. A process for forming an SiC ingot in an apparatus comprising a crucible having; a first enclosure defined by a bottom, a cover and at least one interior sidewall and in which a SiC nucleus is positioned, each of the three crucible components being formed from a material selected from the group consisting of graphite, TiC, HfC, TaC and MoC; a SiC powder reservoir located within the first enclosure which provides a first SiC source; a second exterior sidewall, said first interior wall and said second exterior wall defining a clearance which is filled with SiC as a second SiC source; and a means for establishing at least one temperature gradient between the SiC nucleus and the first and second SiC sources, the process, comprising: a) placing said SiC nucleus in said first enclosure;   b) forming a vacuum within said first enclosure;   c) cleaning said nucleus by establishing the temperature relationships Tg>Ts and Tg>Tc, wherein temperatures Tg, Ts and Tc respectively are of the nucleus, the SiC material within said first enclosure and the SiC material within said clearance; and   d) growing a body of SiC on said nucleus by establishing the temperature relationships: Ts>Te>Tg, wherein Tg, Ts and Tc are as defined above.